<template>
  <div class='xtx-carousel' @mouseleave="start" @mouseenter="stop">
    <ul class="carousel-body">
        <!-- 轮播图的每一项 -->
      <li class="carousel-item" v-for="(item,i) in sliders" :key="i" :class="{fade:index===i}">
          <!-- to的路径不是固定的 -->
        <RouterLink to="/">
          <img :src="item.imgUrl" alt="">
        </RouterLink>
      </li>
    </ul>
    <a href="javascript:;" class="carousel-btn prev"><i class="iconfont icon-angle-left"></i></a>
    <a href="javascript:;" class="carousel-btn next"><i class="iconfont icon-angle-right"></i></a>
    <div class="carousel-indicator">
      <span v-for="(item,i) in sliders" :key="i" :class="{active:index===i}"></span>
    </div>
  </div>
</template>

<script>
// 通用的轮播图组件
// 1 自动轮播
// 2上一张下一张
// 3指示器确定
// 鼠标放上暂停，鼠标移走恢复自动
import { ref, watch } from 'vue'
export default {
  name: 'XtxCarousel',
  props: {
    // 轮播图接收的数据
    sliders: {
      type: Array,
      default: () => []
    },
    autoplay: {
      type: Boolean,
      default: false
    },
    during: {
      type: Number,
      default: 1
    }
  },
  setup (props) {
    // setup函数有两个参数 props emits
    // 轮播图初始的展示的图片下标
    const index = ref(0)
    // 自动播放
    let timer = null
    const autoPlayFn = () => {
      // 清除其他的定时器
      clearInterval(timer)
      timer = setInterval(() => {
        index.value++
        if (index.value >= props.sliders.length) {
          index.value = 0
        }
      }, props.during * 1000)
    }
    // 侦听器侦听props.sliders 当数据发生改变的时候，触发后面的回调函数
    watch(() => props.sliders, (newvalue) => {
      // 有数据并且开启自动轮播，才调用函数
      if (props.autoplay && newvalue.length > 1) {
        index.value = 0
        autoPlayFn()
      }
    })
    // 鼠标移入暂停，鼠标移出恢复
    const start = () => {
      // 鼠标移出恢复定时器
      if (props.sliders.length && props.autoPlay) {
        autoPlayFn()
      }
    }
    const stop = () => {
      // 鼠标移入停止定时器
      if (timer) {
        clearInterval(timer)
      }
    }
    return { index, start, stop }
  }
}
</script>
<style scoped lang="less">
.xtx-carousel{
  width: 100%;
  height: 100%;
  min-width: 300px;
  min-height: 150px;
  position: relative;
  .carousel{
    &-body {
      width: 100%;
      height: 100%;
    }
    &-item {
      width: 100%;
      height: 100%;
      position: absolute;
      left: 0;
      top: 0;
      opacity: 0;
      transition: opacity 0.5s linear;
      &.fade {
        opacity: 1;
        z-index: 1;
      }
      img {
        width: 100%;
        height: 100%;
      }
    }
    &-indicator {
      position: absolute;
      left: 0;
      bottom: 20px;
      z-index: 2;
      width: 100%;
      text-align: center;
      span {
        display: inline-block;
        width: 12px;
        height: 12px;
        background: rgba(0,0,0,0.2);
        border-radius: 50%;
        cursor: pointer;
        ~ span {
          margin-left: 12px;
        }
        &.active {
          background:  #fff;
        }
      }
    }
    &-btn {
      width: 44px;
      height: 44px;
      background: rgba(0,0,0,.2);
      color: #fff;
      border-radius: 50%;
      position: absolute;
      top: 228px;
      z-index: 2;
      text-align: center;
      line-height: 44px;
      opacity: 0;
      transition: all 0.5s;
      &.prev{
        left: 20px;
      }
      &.next{
        right: 20px;
      }
    }
  }
  &:hover {
    .carousel-btn {
      opacity: 1;
    }
  }
}
</style>
